*Other
set times may also be available. Call your sales representative for
more information.

General Directions and Guidelines

Preparing
the Mix

Use
potable water at temperatures between 70° and 100°F (21° and
38°C). Since variations in slurry (HYDROCAL® Brand White
Gypsum Cement and water mixture) temperature produce variations in setting
time, it is important to keep both HYROCAL Brand White Gypsum Cement and
water in a stable temperature environment prior to use. The higher the temperature
of the slurry, the shorter the set time. See the graph below.

Measuring

Weigh both
HYDROCAL Brand White Gypsum Cement and water at the recommended use consistency
for each mix (see Technical Properties above). The water-to-HYDROCAL Brand
White Gypsum Cement ratio is critical because it governs all physical properties
of the final cast piece.

Soaking

Sift or
strew HYDROCAL Brand White Gypsum Cement into water slowly and evenly. Do
not drop handfuls of HYDROCAL Brand White Gypsum Cement directly into the
water. Allow soaking for 1-2 minutes. HYDROCAL Brand White Gypsum Cement
should be fully dispersed in the water prior to mixing. Small batches require
less soaking than large batches.

Mixing

Mixing the HYDROCAL
Brand White Gypsum Cement slurry is one of the most important steps in
producing HYDROCAL Brand White Gyspum Cement casts with maximum strength,
hardness, and other important properties.

Mechanically mixed
slurries develop uniform casts with optimal strengths. HYDROCAL Brand
White Gypsum Cement can be mechanically mixed through both batch and continuous
processes. Proper blade and bucket dimensions are important for obtaining
the best batch mix. Longer mixing times result in higher cast strength
and shorter setting times. The relationship between mixing time and both compressive
strength and setting time is shown below.

Pouring

To prevent air entrainment
and provide a uniform, smooth surface, careful pouring of the slurry is
necessary. Agitation of the filled mold is a further step used to prevent
air at or near the surface of the cast piece. Whenever possible, the slurry
should be poured carefully in the deepest area so the slurry flows evenly
across the surface of the mold.

Pouring a large amount
of slurry directly on the face of the mold may result in slight densification
of the cast at the point where the slurry strikes the surface of the mold.

Drying

All casts should be
dried as quickly as is safely possible after manufacture so that maximum
physical properties can develop. Dry to a constant weight.

The best drying rooms
or ovens provide (1) uniform and rapid circulation (minimum of 15-30 fps)
of air with no dead spots having little or no air movement, (2) equal
temperatures throughout the entire area, and (3) provisions for exhausting
a portion of the air while replacing it with fresh air. High humidity
surrounding the drying room or oven inhibits the efficiency of the drying
because the air pulled into the room is incapable of picking up much moisture
from the cast pieces.

The maximum temperature
at which HYDROCAL Brand White Gypsum Cement casts are safe from calcination
is 120°F (49°C). With substantial free water in the cast piece,
higher drying temperatures can be used without difficulty. As drying progresses,
the temperature must be reduced to prevent calcination. The safe drying
zone is in the shaded area of graph (below, right). Before removing casts
from the dryer, the temperature should approach that of the area around
the dryer to prevent thermal shock.

Storage

Keep
in a dry, stable environment indoors. Do not stack more than 2 pallets high.
Keep from drafts. Rotate stock.